Other versions exist on this site from various publications. This one is from the Radio Electronics Experimenter from 1990. The bargraph circuit uses the UAA170.
In the figure we have an astable multivibrator driving a speaker to produce audio signals for...
This circuit, which we found in an Argentine publication from the 1970s, uses a large high voltage...
This circuit is from a 1965 General Electric hobby manual. The circuit can be assembled with...